Developmental assessment of human vitrified-warmed blastocysts based on oxygen consumption

Background: In this study, we aimed to develop a model for embryo selection based on oxygen consumption following cryopreservation, the relationship between the developmental competence of blastocysts and their oxygen consumption was assessed.Methods: Oxygen consumption of vitrified-warmed human blastocysts was measured at 0, 1.5, 3, 4.5, 6, 7.5, 9 and 24 h after warming using scanning electrochemical microscopy. On the basis of their developmental stage at 24 h, blastocysts were classified into four groups (hatched, hatching, arrested and degenerated). Moreover, cytochrome c oxidase (CCO) activity in vitrified-warmed blastocysts was assessed at 0 and 24 h.Results: The oxygen consumption rate of blastocysts just after warming was significantly lower than that of non-vitrified blastocysts (P< 0.05). The oxygen consumption rate of blastocysts was significantly higher in the hatched group than in the arrested and the degenerated groups after 1.5 h (P< 0.05) and than in the hatching group (P< 0.05) at 7.5 and 9 h. Moreover, CCO activity was absent in vitrified-warmed blastocysts at 0 h, but was detected at 24 h. Conclusions: The respiratory rate of vitrified blastocysts after warming was significantly lower than non-cryopreserved blastocysts. Oxygen consumption of blastocysts with high developmental potential was restored earlier than that of blastocysts with low developmental potential. The Results: of this study suggest that it is possible to select vitrified-warmed blastocysts with high developmental potential based on their respiratory activity.